diff --git a/src/libsystemd/sd-daemon/sd-daemon.c b/src/libsystemd/sd-daemon/sd-daemon.c
index 27045e25d0..a48fa05908 100644
--- a/src/libsystemd/sd-daemon/sd-daemon.c
+++ b/src/libsystemd/sd-daemon/sd-daemon.c
@@ -586,7 +586,7 @@ _public_ int sd_watchdog_enabled(int unset_environment, uint64_t *usec) {
         r = safe_atou64(s, &u);
         if (r < 0)
                 goto finish;
-        if (u <= 0) {
+        if (u <= 0 || u >= USEC_INFINITY) {
                 r = -EINVAL;
                 goto finish;
         }